1. Field of the Invention
The present invention relates to a golf club.
2. Description of the Related Art
In aspects of development and sales of golf clubs, evaluations of head performance and shaft performance have been made. Methods of these evaluations involve hitting by a tester, hitting with a swing robot, and the like.
When comparison of shaft performances is intended, a head attached to this shaft is preferably of the same kind. By using the heads of the same kind, influences from the difference in the head can be minimized, whereby the shaft performance can be accurately compared. For example, when three kinds of shafts are subjected to a comparative test, the heads of the same kind are attached to the three kinds of the shafts, respectively, and then the comparative test is carried out.
However, even though the heads of the same kind are used, there exit inevitably variances of performances among these heads in a strict sense. In order to compare the shaft performance more accurately, it is preferred to conduct the test with the identical head to be sequentially attached to each shaft.
The same is applied to the comparative test of head performances. Even though the shafts of the same kind are attached to the heads, respectively, there exit inevitably variances of performances among these shafts in a strict sense. In order to compare the head performance more accurately, it is preferred to conduct the test with the identical shaft to be sequentially attached to each head.
Therefore, when the head performances and shaft performances are evaluated, it is preferred that attachment/detachment of the shaft and the head can be easily conducted.
Ease in attachment/detachment of the head and shaft can be beneficial in a variety of aspects. When the attachment/detachment can be easily conducted, golf players can easily change the shaft or the head by themselves. For example, the golf player who cannot feel satisfaction with performances of purchased golf club can easily change by oneself the shaft or the head. In addition, easy construction of an original golf club including a desired head in combination with a desired shaft is enabled by the golf players themselves. The golf players may purchase a desired head and a desired shaft, and can themselves construct with these parts. The head and shaft which can be easily attached/detached enables custom fabrication of the golf club.
In general, the head and the shaft are adhered with an adhesive. For separation of the adhered head and shaft, it is necessary to pull the shaft out from the shaft hole by a strong external force while allowing for thermal degradation of the adhesive by heating the joint portion at a high temperature. This operation requires efforts, equipments and time. Additionally, during heating or pulling out, the shaft or the head can be damaged. Accordingly, attachment/detachment of the head and the shaft is not easy in general.
In view of the foregoings, United States Patent Application Serial No. US2006/0293115 A1 discloses a structure in which attachment/detachment of the head and the shaft is facilitated.